CN1167314C

CN1167314C - Screen printing method and screen printing apparatus

Info

Publication number: CN1167314C
Application number: CNB971954348A
Authority: CN
Inventors: 和智昭彦; 志郎; 梁池征志郎; 幸; 柿岛信幸; 也; 松本昌也
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1996-06-14
Filing date: 1997-06-12
Publication date: 2004-09-15
Anticipated expiration: 2017-06-12
Also published as: WO1997048258A1; JP2000514005A; DE69703350D1; CN1221552A; EP0904675A1; EP0904675B1; DE69703350T2; US6131511A

Abstract

Coordinate positions of openings and lands on a screen (121) and a first circuit board (150) are recognized by a recognition camera (2) and a display device (111). A correction amount for move of the stage (1) is calculated by a control device (110) only for the first circuit board. Then, the correction of move of the stage (1) is executed for the second and following circuit boards (153) by utilizing the correction amount.

Description

Screen printing method and screen printing apparatus

The present invention relates to a screen printing method and a screen printing apparatus for performing printing on a circuit board by using one screen.

Referring to fig. 7 to 9, which illustrate a screen printing apparatus according to the prior art, fig. 10 is a flowchart of a screen printing method according to the prior art. The screen printing method used in the prior art is described below.

The screen printing apparatus 30 is given as an apparatus for printing solder paste on a printed board 50 equivalent to a circuit board, and includes an identification device 10 and a printing device 20. As shown in fig. 7.

The identification device 10 comprises a stage 1; motors 3 to 5 for moving the stage 1 in directions X, Y and θ as shown; an identification camera 2 for discriminating the

identification marks

51, 52 drawn on the printing plate 50 and the

identification marks

24, 25 on the screen 21; a control device 6, which identifies the camera 2 and the motors 3 to 5 by electrical connection.

The printing apparatus 20 comprises a screen 21 on which a pattern showing the layout of a mesh for printing solder paste onto the printing plate 50; a squeegee 22 for applying the flux 23 on the screen 21 to the entire surface of the screen 21.

The control device 6 controls the driving of the motors 3 to 5 based on the information obtained from the recognition camera 2 so that the mesh pattern on the screen 21 matches the corresponding pattern of printing positions on the printing plate 50 so that the corresponding pattern can be printed on the printing plate 50.

The screen printing apparatus 30 includes: the stage 1 reciprocates between a printing plate loading/unloading position 182 and a position 183 directly below the screen (the stage 1 in this position is located directly below the screen 21 and fixed relatively to the screen 21). Thus, the printing operation is performed in accordance with the steps shown in fig. 10.

More specifically, (step is represented by "S" in the drawing) step 1, the printing plate 50 is placed at the printing plate loading/unloading position 182 of the stage 1; steps 2 to 4, obtaining a position adjustment of the printing plate 50 with respect to the screen plate 21, which will be described in detail below; the following step 5, the stage 1 moves to a position 183 directly below the screen plate and then moves upward to the screen plate 21; step 6, the screen 21 and the printing plate 50 are contacted with each other, completing the printing. In this printing process, the squeegee 22 is moved left or right in the drawing, and by this means, the flux 23 can be printed on the printing plate 50 in a mesh pattern on the screen 21; at step 7 after printing, the stage is lowered from a position directly below the screen 183 back to the printing plate loading/unloading position 182 again. After the printing process is completed, the printed plate is removed from the stage 1, another printing plate to be printed is placed on the stage 1, and the above steps are repeated.

Now, in steps 2 to 4, the position adjustment of the printing plate 50 is explained.

The position adjustment is to adjust the position of the printing plate 50 with respect to the screen 21 so that the printed printing plate is placed at a specific position with respect to the fixed screen 21. The position adjustment information can be obtained by discriminating the

identification marks

24, 25 on the screen plate 21 and the

identification marks

51, 52 on the printing plate 50. This can be done by moving the recognition camera 2. A detailed description will be given below with reference to fig. 11 to 12.

First, the identification marks 24, 25 on the discrimination net plate 21 are explained. The distance of the start point 2a of the recognition camera 2 with respect to the recognition mark 24 (SX1, SY1), and the distance of the start point 2a of the recognition camera 2 with respect to the recognition mark 25 (SX2, SY2) can be calculated by the following equation [1 ]:

SX1＝Sx1+Cx1×SCx1

SY1＝Sy1+Cy1×SCy1

SX2＝Sx2+Cx1×SCx2

SY2＝Sy2+Cy1×SCy2 .....[1]

wherein,

when the camera origin 2a is set as the origin of the X-Y coordinate axis, Sx1 and Sx2 are coordinate values of the

recognition marks

24 and 25 in the X direction, respectively.

When the camera origin 2a is set as the origin of the X-Y coordinate axis, Sy1 and Sy2 are coordinate values of the identifying

marks

24 and 25 in the Y direction, respectively.

Cx1 is the resolution of the recognition camera 2 in the X direction, and Cy1 is the resolution of the recognition camera 2 in the Y direction.

SCx1, SCx2 is the number of pixels in the effective field of view in the X direction relative to the identifying

marks

24, 25, respectively.

SCy1, SCy2 are the number of pixels in the effective field of view in the Y direction relative to the identifying

marks

24, 25, respectively.

The distance from the camera start point 2A to the midpoint of the

identification marks

24, 25 is (SMX, SMY). θ s is defined as an inner angle between a straight line connecting the

identification marks

24, 25 and a straight line parallel to the X-axis. Also, the distances (SMX, SMY) and the angle θ s described above represent the target position.

Next, when the stage 1 is located at the printing plate loading/unloading position 182 and moved to the position 183 directly below the stencil, respectively, one of the identification marks 60 on the stage 1 is identified. Thus, the moving amount (LX, LY) of the stage 1 can be calculated.

After these operations are completed, the

identification marks

51, 52 on the printing plate 50 are identified. To realize such a recognition operation, as with the recognition marks 24, 25 on the screen plate 21 described above, the distances (PX1, PY1), (PX2, PY2) from the start point 2A of the camera to the

recognition marks

51, 52 shown in fig. 12 can be calculated by the following equation:

PX1＝Px1+Cx1×PCx1

PY1＝Py1+Cy1×PCy1

PX2＝Px2+Cx1×PCx2

PY2＝py2+Cy1×PCy2 ....[2]

where Px1 and Px2 are coordinate values on the X axis of the

identification marks

51 and 52, respectively, when the camera origin 2a is set as the origin of the X-Y coordinate axis;

py1 and Py2 identify the coordinate values of the

marks

51 and 52 on the Y axis when the camera origin 2a is the origin of the X-Y coordinate axis;

PCx1, PCx2 are the number of pixels in the effective field of view in the X direction relative to the

identification marks

51, 52, respectively;

PCy1, PCy2 are the number of pixels in the effective field of view in the Y direction relative to the identifying

marks

24, 25, respectively;

the distance from the camera starting point 2a to the midpoint of the

recognition marks

51 and 52 is (PMX, PMY). An inner angle formed by a straight line connecting the

identification marks

51, 52 and a straight line parallel to the X axis is set to θ p.

Based on these statements, the order of the operations of the identification and adjustment of the printing plate is thus explained. A new printing plate 50-1 is taken in, placed on the stage 1, the camera 2 is identified, and the position of the printing plate 50-1 with respect to the previously described positions (PX1, PY1), (PX2, PY2) is determined by the control device 6. In the same manner as the recognition operation on the printed board 50, the recognition marks 51-1, 51-2 on the printed board 50-1 are respectively recognized by the recognition cameras 2, so that the midpoints (PMX-1, PMY-1) between the two points and θ p-1 are respectively determined. The distances (PX1-1, PY1-1), (PX2-1, PY2-1) from the origin 2a of the camera to the identification marks 51-1, 52-1 can be calculated by the following equation:

PX1-1＝Px1+Cx1×PCx1-1

PY1-1＝Py1+Cy1×PCy1-1

PX2-1＝Px2+Cx1×PCx2-1

PY2-1＝Py2+Cy1×PCy2-1

wherein PCx1-1, PCx2-1 is the number of pixels in the effective visual field range in the X direction with respect to the identification mark 51-1, 52-1, respectively.

PCyl-1, PCy2-1 are the number of pixels in the effective visual field range in the Y direction with respect to the identification mark 51-1, 52-1, respectively. Simultaneously, the method comprises the following steps:

PMX-1＝{(PX2-1)-(PX1-1)}/2

PMY-1＝{(PY2-1)-(PY1-1)}/2

the movement of the previous stage (LX, LY) is added to the midpoint (PMX-1, PMY-1) to calculate the position of printing plate 50-1 on printing device 10.

Therefore, the amount of movement of the stage 1 with respect to the printing plate 50-1 is compared with the case where the printing plate 50 is placedIs determined by the following equation:

based on the amount of movement () When the movement of the stage 1 is controlled, the stage 1 is moved to the printing apparatus 20.

As described above as the screen printing apparatus of the prior art, the position adjustment of the printing plate 50 is performed by recognizing the mark on the screen 21 and the mark on the printing plate 50 and moving to the screen 21, thereby completing the entire printing process. The apparatus has a drawback in that it cannot be applied to a plate such as the printing plate 50 having no identification mark.

Further, in the screen printing apparatus of the prior art described above, only one printing plate 50 can be placed on the stage 1 at a time, and the position adjustment is performed each time the printing plate 50 is placed, but the difference in the placement position of each printing plate 50 on the stage 1 during the printing process is small and it is not necessary to perform the adjustment each time. Therefore, the printing apparatus of the related art performs unnecessary steps for each printing plate, which leads to an unnecessary increase in the required printing time of the printing plate.

The present invention addresses the above-mentioned deficiencies and others. It is an object of the present invention to provide a screen printing method and a screen printing apparatus capable of performing a printing operation at a speed higher than that of the prior art, and a further object of the present invention is to provide a screen printing method and a screen printing apparatus capable of being used for a screen and a printing plate having no identification mark.

To achieve these objects, according to a first aspect of the present invention, there is provided a screen printing method performed by a screen printing apparatus including a screen and a stage. In this device, the circuit boards are sequentially placed on the same mounting position of the stage. In such board loading/unloading positions, the circuit board is not covered by the screen; at least one of the stage and the screen is movable so that the circuit board and the screen can be covered with each other, and also the solder on the screen can be printed on the circuit board in turn.

A method of screen printing comprising the steps of: placing a circuit board on a mounting position of an objective table of a screen printing device so that the circuit board is not overlapped with a screen of the screen printing device; when the screen plate is placed, the installation position of the screen plate relative to an identification reference point is identified by detecting any two different points on the screen plate and calculating the positions of the two points on the screen plate relative to the identification reference point; when the circuit board is placed on the objective table, the position adjustment amount for re-placing at least one of the screen plate and the circuit board is calculated according to the mounting position of the identified screen plate and the mounting position of the circuit board by detecting two different points corresponding to the two points on the screen plate on the circuit board and calculating the positions of the two points on the circuit board relative to the identification reference point; and

moving at least one of the stage and the screen such that the screen and the circuit board overlap each other; wherein at least one of the stage and the screen is moved according to a position adjustment amount each time the same type of circuit board is placed on the stage; applying a flux on the screen; the solder paste is printed from a screen onto a circuit board that overlaps the screen.

According to a second aspect of the invention, there is provided a screen printing method performed by a screen printing apparatus comprising a screen and a stage. In this device, the circuit boards are sequentially placed on the same mounting position of the stage. In such board loading/unloading positions, the circuit board is not covered by the screen; at least one of the stage and the screen is movable so that the circuit board and the screen can be covered with each other, and the solder paste on the screen can be printed on the circuit board in turn.

The screen printing method comprises the following steps:

when the screen is mounted on the screen printing device, identifying a mounting position of the screen relative to an identification reference point;

when the circuit board is placed on the object stage, identifying a placement position of the circuit board relative to an identification reference point;

according to the recognized installation position of the screen plate and the placement position of the circuit board, the position adjustment amount of the screen plate and the circuit board can be calculated, the screen plate or the objective table is moved by considering the position adjustment amount, so that the screen plate and the circuit board can be mutually covered, and the welding flux on the screen plate is printed at the pattern printing position of the circuit board.

According to a third aspect of the invention, a screen printing method according to the first or second aspect is proposed. The identification of the installation position of the screen plate is completed by adopting the following method: any two different points on the screen are detected, and the positions of the two points relative to the identification reference point are calculated. Meanwhile, the identification of the circuit board mounting position is completed by adopting the following method: any two different points on the circuit board are detected, and the positions of the two points relative to the identification reference point are calculated.

According to a fourth aspect of the invention, a screen printing method according to the third aspect is proposed. Wherein any two different points on the screen plate are any two different meshes on the screen plate

According to a fifth aspect of the invention, a screen printing method according to the third or fourth aspect is proposed. Wherein any two different points on the circuit board are any two different contact points on the circuit board.

According to a sixth aspect of the invention, there is provided a screen printing method according to any one of the first five aspects. Wherein, given a reference state: the amount of adjustment for the solder paste on the screen to be printed to the position of the pattern on which the circuit board should be printed can be calculated based on the following factors:

displacement between the position of the screen plate and the installation position of the screen plate in a reference state;

the displacement between the position of the circuit board in the reference state and the placement position of the circuit board.

According to a seventh aspect of the present invention, there is provided a screen printing apparatus comprising a screen and a stage. In this device, the circuit boards are sequentially placed on the same mounting position of the stage. In such board loading/unloading positions, the circuit board is not covered by the screen; at least one of the stage and the screen is movable so that the circuit board and the screen can be covered with each other, and also the solder on the screen can be printed on the circuit board in turn.

The screen printing apparatus was composed as follows:

an object stage for placing the circuit board; a moving device for moving at least the stage and the screen plate so that the screen plate and the circuit board mounted by the stage overlap each other, and

a printing device for printing the flux of the screen plate on the circuit board,

an image pickup device for recognizing a mounting position of the screen plate with respect to an identification reference point by detecting any two different points on the screen plate and calculating positions of the two points on the screen plate with respect to the identification reference point when the screen plate is mounted, and recognizing a mounting position on the circuit board (150) with respect to the identification reference point by detecting two different points on the circuit board corresponding to the two points on the screen plate and calculating positions of the two points on the circuit board (150) with respect to the identification reference point when the circuit board is mounted on the stage; and a control device for calculating a position adjustment amount for repositioning at least one of the screen and the circuit board according to the recognized mounting position of the screen and the mounting position of the circuit board, and if the same type of circuit board is placed on the stage, the moving device moves at least one of the stage and the screen according to the adjustment amount.

According to an eighth aspect of the present invention, there is provided a screen printing apparatus comprising a screen and a stage. In the apparatus, circuit boards are sequentially placed on the same placing position of the stage, and at such board loading/unloading position, the circuit boards are not covered by the screen; at least one of the stage and the screen is movable so that the circuit board and the screen can be covered with each other, and also the solder on the screen can be printed on the circuit board in turn.

The screen printing apparatus was composed as follows:

an image pickup device for recognizing a mounting position of the screen with respect to a recognition reference point when the screen is mounted to the screen printing apparatus; when the circuit board is placed on the stage, it is used to identify a placement position of the circuit board relative to an identification reference point.

And the control equipment can calculate the position adjustment amount of the screen plate and the circuit board according to the identified mounting position of the screen plate and the mounting position of the circuit board, and then sequentially place the circuit boards of the same type on the objective table, and only one circuit board of the same type is placed on the objective table every time. The screen or the stage is moved so that the screen and the circuit board can be overlaid on each other in consideration of the position adjustment amount, and the solder on the screen is printed to the pattern printing position of the circuit board.

According to a ninth aspect of the present invention, there is provided a screen printing apparatus according to the seventh or eighth aspect. The image pickup equipment identifies the installation position of the screen plate and adopts the following method to complete the process: any two different points on the screen are detected, and the positions of the two points relative to the identification reference point are calculated. Meanwhile, the image shooting equipment identifies the circuit board placing position and adopts the following method to complete the process: any two different points on the circuit board are detected, and the positions of the two points relative to the identification reference point are calculated.

According to a tenth aspect of the present invention, there is provided a screen printing apparatus according to the ninth aspect. Wherein any two different points on the screen plate identified by the image pickup device are any two different meshes on the screen plate.

According to an eleventh aspect of the present invention, there is provided a screen printing apparatus according to the ninth or tenth aspect. Wherein any two different points on the circuit board that are recognized by the image capture device are any two different contact points on the circuit board.

According to a twelfth aspect of the present invention, there is provided a screen printing apparatus comprising a screen and a stage. In the apparatus, circuit boards are sequentially placed on the same placing position of the stage, and at such board loading/unloading position, the circuit boards are not covered by the screen; at least one of the stage and the screen is movable so that the circuit board and the screen can be overlaid on each other, so that the solder paste on the screen can be printed on the circuit board in turn.

The screen printing apparatus was composed as follows:

an image pickup device for obtaining image data of any one of designated places on the screen or on the circuit board by moving the image pickup device when the circuit board is placed on the stage, thereby identifying a mounting position on the screen with respect to the identification reference point and a mounting position on the circuit board with respect to the identification reference point; and

a control device for printing the solder on the screen plate to the pattern printing position on the circuit board, the required displacement adjustment amount can be obtained by calculating the adjustment amount of the screen plate or the circuit board position through the control device,

wherein, given a reference state: the amount of adjustment for the solder paste on the screen to be printed to the position of the pattern on which the circuit board should be printed can be calculated based on the following factors:

a displacement between the position of the circuit board in the reference state and the placement position of the circuit board.

Brief description of the drawings:

the various aspects and features of the present invention will become more apparent in light of the following description of preferred embodiments with reference to the accompanying drawings. Wherein:

FIG. 1 is a flow chart illustrating the operation of a screen printing method according to a first embodiment of the present invention;

FIG. 2 is an illustration of a method of determining stage movement adjustments in the flowchart of FIG. 1;

FIG. 3 is a flowchart of FIG. 1 showing an example of a method for identifying a screen mounting position and a circuit board mounting position;

FIG. 4 is another example of the method for identifying the screen mounting position and the circuit board mounting position in the flowchart of FIG. 1;

FIG. 5 is a block diagram of electrical connections of the control device shown in FIG. 2, a recognition camera, and the like;

FIG. 6 is an explanation of a method of determining the stage movement adjustment amount in the flowchart of FIG. 1;

FIG. 7 is an overall view of the screen printing apparatus;

FIG. 8 is a plan view of a stage and the like in a screen printing apparatus according to the prior art;

FIG. 9 is a view showing a screen or the like in a screen printing apparatus according to the prior art;

FIG. 10 is a flow chart of the operation of a prior art screen printing method;

FIG. 11 is an explanation of a method of determining the stage movement adjustment amount in the flowchart of FIG. 10;

FIG. 12 is an explanation of a method of determining the stage movement adjustment amount in the flowchart of FIG. 10;

fig. 13 is an operation flowchart of a screen printing method as another embodiment of the present invention.

Before explaining the present invention, it should be noted that like reference numerals represent like parts throughout the drawings.

A screen printing method and a screen printing apparatus 100 according to an embodiment of the present invention will be described below with reference to the drawings. It should be noted that like reference numerals refer to like parts. Also, the screen printing method is performed by the screen printing apparatus 100.

When the screen and the circuit board are overlapped with each other, the solder is printed to a pattern printing position of the circuit board through a mesh pattern on the screen by taking the solder as an example, and the pattern printing position refers to a printing position to which the solder should be reached by a contact point pattern of the circuit board. In this manner, the state of being printed to the position of the pattern to be printed on the circuit board in the mesh pattern of the screen is taken as the reference state. In the screen printing method and the screen printing apparatus of the embodiment of the invention, the placement adjustment amounts of the screen mounted on the screen printing apparatus and the circuit board in the reference state are calculated. After the calculation, the printing operations on the circuit boards can be sequentially performed based on the calculated adjustment amounts without calculating the adjustment amounts for each circuit board. In this respect, the adjustment amount is calculated based on the displacement between the screen position and the screen mounting position in the reference state, and the displacement between the adjustment amount calculation circuit board position and the placement position of the adjustment amount calculation circuit board on the stage in the reference state.

Further, the adjustment amount calculating circuit board refers to any one of the same kind of circuit boards that need to be printed. A circuit board that is used to calculate screen and circuit board adjustments is needed for printing a mesh pattern on a screen to a location on the circuit board where the pattern should be printed.

The screen printing apparatus 100 is similar in composition to the screen printing apparatus 30 of the prior art previously described. More specifically, as shown in fig. 2 and 5, the screen printing apparatus 100 includes a screen 121, a stage 1, a recognition camera 2 functioning as an image pickup device, motors 3 to 5, and a control device 110 for controlling the motors 3 to 5 and electrically connected to the recognition camera 2 and an NC section 312. However, the screen printing apparatus 100 can be used for the screen 121 and the circuit board without the identification mark, compared to the conventional screen printing apparatus. To achieve this, a display device 111 is electrically connected to the control device 110. The display device clearly displays the mesh pattern on the screen 121 and the position pattern of the contact points on the circuit board, all of which are photographed by the recognition camera 2.

Further, in the screen printing apparatus 100, it is assumed that circuit boards to be placed one by one on the stage 1 are always placed at the same position of the stage.

Now, referring to fig. 6, a method of calculating the adjustment amount is summarized. For simplicity of explanation, it is assumed that the adjustment amount calculation circuit board 150 moves relative to the screen mounted on the screen printing apparatus so as to be placed in the reference state. The X-Y coordinates have an identification reference point 181 as the origin of coordinates.

First, two

points

201 and 202 are arbitrarily selected on the screen 121 of the screen printing apparatus, and then, the positions of the two

points

201 and 202 with respect to the 181 identifying the reference point are identified. Based on the position information identifying the point 201 and the point 202, the position information of the midpoint 203 of the point 201 and the point 202 can be calculated. Similarly, an angle θ s formed by a line connecting the point 201 and the point 202 and a reference line parallel to the X-axis can be calculated.

Also, as for the adjustment amount calculating circuit board placed on the stage 1, two

points

221 and 222 on the adjustment amount calculating circuit board 150 are arbitrarily selected, and the positions of the

points

221 and 222 with respect to the identification reference point 181 are identified. Based on the location information identifying point 221 and point 222, the location information of midpoint 223 of point 221 and point 222 may be calculated. Also, an angle θ p formed by a connecting line of the point 221 and the point 222 and a reference line can be calculated.

It is assumed that, when the screen board 121 and the adjustment amount calculation circuit board 150, as described above, are placed in the reference state, the mutual distances of the middle point 203 and the middle point 223 are represented by X0 in the X direction and Y0 in the Y direction; their mutual displacement is represented by the angle θ 0 in the angular direction, as shown in fig. 6. And the values of X0, Y0, θ 0 are equivalent to the adjustment amounts.

Thus, once the adjustment amounts X0, Y0, θ 0 are determined; calculating position information of the midpoint 223 of the circuit board 150 with respect to the adjustment amount placed on the stage 1, the stage moving distance being X0, Y0; then, the stage 1 is rotated by an angle θ 0 with respect to the angle information θ p of the adjustment amount calculation circuit board 150. As in the prior art example, the stage 1 is moved toward the screen 121 by the amount LX, LY, so that the screen 121 and the adjustment amount calculation circuit board 150 are placed in the reference state. By this method, the moving amount by which the screen plate 121 and the adjustment amount circuit board 150 are placed in the reference state can be obtained by adding the moving amounts LX, LY to the adjustment amounts X0, Y0, θ 0.

Subsequently, the circuit boards 153, which are mounted on the stage 1 in turn, are assumed to be mounted on the stage 1 at the same positions where the adjustment amount circuit boards 150 were mounted. Also, the mesh plate 121 is fixed. Once the adjustment amount is determined by using the adjustment amount calculation circuit board 150, it is not necessary to calculate the adjustment amount for each circuit board 153. Therefore, when placing each circuit board 153 to the stage 1, the stage 1 is moved with the position information of the midpoint 223, which has been stored as the position information, as an adjustment amount; and the stage 1 is moved according to a known movement amount so that each circuit board 153 will be placed in a reference state with respect to the screen 121.

Next, in the following case, an explanation is given to a specific method of calculating the movement amount. This case means that: the adjustment amount (X0, Y0 as described above) is equivalent to the midpoint displacement amount when the screen plate 121 and the adjustment amount calculation circuit board 150 are placed in the reference state, and also the adjustment amount (θ 0 as described above) is equivalent to the displacement amount whose angular direction has been determined, so moving the stage 1 toward the screen plate 121 according to the amount of movement will cause the screen plate 121 and the adjustment amount circuit board 150 to be placed in the reference state.

The operation of the screen printing apparatus 100 thus constituted is explained below with reference to fig. 1.

In step 201, a new screen 121 is mounted on the printing apparatus 120, and an adjustment amount calculating circuit board 150, which is a first circuit board to be printed by the new screen 121, is mounted on the stage 1. Note that; the adjustment amount calculation circuit board 150 is not necessarily limited to only one board with respect to the new screen 121, and one adjustment amount calculation circuit board may be used for each printing. For example, the same screen can be used to complete 1000 circuit board prints.

In step 202, an identification of a mounting location on the screen 121 is performed. More specifically, as described above, since the mesh panel 121 does not have the identification mark as in the prior art, the operator can arbitrarily select the

meshes

122, 123 from the mesh pattern of the mesh panel 121. The identification camera is then moved towards the

meshes

122, 123. Now taking the mesh 122 as an example, as shown in fig. 3, the middle point of the mesh 122 displayed on the display device is adjusted to coincide with the intersection 111A on the screen of the display device 111. When the midpoint of the cell 122, and the intersection 111A coincide with each other, the control device 110 measures the distances in the X and Y directions, identifying the distance of the reference point 181 with respect to the cell 122. Also, for mesh 123, similar operations are performed. Suppose the distance of the cells 122 is (SX1, SY 1); assuming that the distances of the cells 123 are (SX2, SY2), these distances (SX1, SY1), (SX2, SY2) can be calculated by the following equation:

SX1＝Sx1

SY1＝Sy1

SX2＝Sx2

SY2＝Sy2 ...[3]

wherein Sx1, Sx2 are coordinate values of the

meshes

122, 123 in the X direction, respectively, when the reference point 181 is identified as the origin of the X-Y coordinate axis; when the reference point 181 is identified as the origin of the X-Y coordinate axis, Sy1, Sy2 are coordinate values of the

meshes

122, 123 in the Y direction, respectively. The calculation equation [3] is obtained by removing (Cx1 × SCx1), (Cy1 × SCy1), (Cx1 × SCx2), (Cy1 × SCy2) from the calculation equation [1] of the prior art. Wherein the calculation can be performed without recognition training.

Next, in step 203, the mounting position of the adjustment amount calculation circuit board 150 is identified in the same manner as in step 202. More specifically, the operator arbitrarily selects two contact points 151, 152 from the contact point pattern on the adjustment amount calculation circuit board 150. Next, the recognition camera 2 moves toward the contact points 151, 152; the control device 110 measures the distance of the identified reference point 181 with respect to the contact points 151, 152 on the X-axis and Y-axis, respectively, using the methods described above. If the distance of the contact point 151 is set to (PX1, PY1), the distance of the contact point 152 is set to (PX2, PY 2). These distances (PX1, PY1) and (PX2, PY2) can be calculated by the following equation [4 ]:

PX1＝Px1

PY1＝Py1

PX2＝Px2

PY2＝Py2 ..........[4]

wherein, when the reference point 181 is the origin of the X-Y coordinate axis, Px1 and Px2 are coordinate values of the contact points 151 and 152, respectively, in the X-axis direction; when the reference point 181 is taken as the origin of the X-Y coordinate axis, Py1, Py2 are coordinate values of the contact points 151, 152 in the Y-axis direction, respectively;

next, based on the distance information (SX1, SY1) of the cell 122, for example, the coordinate position of the cell 122; likewise, distance information (SX2, SY2) of the cell 123, such as the coordinate position of the cell 123; these have been determined by equation [3] above, and the control device 110 determines a coordinate position (SMX1, SMY1), e.g., the coordinate position of the midpoint of the coordinate positions of the cell 122 and the cell 123. Further, the control device 110 determines a connection line connecting the coordinate positions of the mesh 122 and the mesh 123, and determines an angle θ S1 formed by the X-axis and the straight line. The coordinate positions of the midpoints (SMX1, SMY1), and the angle θ S1 are taken as target values.

Also, in a similar manner, from the distance information (PX1, PY1) of the contact point 151, for example, the coordinate position of the contact point 151; also, distance information (PX2, PY2) of the contact point 152, such as the coordinate position of the contact point 152; having been determined by the above-described equation [4], control device 110 determines a coordinate position (PMX1, PMY1), e.g., the coordinate position of contact point 151 and the coordinate position of the midpoint of the coordinate position of contact point 152. Further, the control device 110 determines a connection line connecting the coordinate positions of the contact point 151 and the contact point 152, and determines an angle θ p1 formed by the X-axis and the straight line.

Next, from the coordinate position (SMX1, SMY1) and the angle θ s1 as the target values of the midpoints, the coordinate position (PMX1, PMY1) and the angle θ p1 of the midpoints of the circuit board 150 are calculated as the adjustment amounts, and these values can be determined by the above description. The control device 110 calculates the amount of movement of the stage 1 toward the reticle 121 based on the information by the following equation [5 ]:

Δx1＝SMX1-(PMX1+LX)

Δy1＝SMY1-(PMY1+LY)

Δθ1＝θs1-θp1 .....[5]

where LX and LY are the moving amounts of the stage described in the prior art example.

It is assumed that the movement amounts Δ x1, Δ y1, Δ θ 1 are always constant for the circuit boards 153, which are sequentially placed on the stage 1 after the adjustment amount calculation circuit board 150.

In step 205, based on the movement amounts (Δ x1, Δ y1, Δ θ 1), the control device 110 controls the operation of the motors 3 to 5 to complete the movement adjustment of the stage 1. After the movement adjustment of the stage 1 is completed, the stage 1 moves to the screen 121 under the operation control of the control device 110, and the printing of the printing adjustment amount calculation circuit board 150 is completed. At step 206, the printed object table 1 is again returned to the printing plate loading/unloading position 182, from where the adjustment quantity circuit board 150 is removed from the object table 1.

At step 207, the circuit board 153 is placed on the stage 1. The movement amount need not be calculated for each board, and as described above, the stage 1 may repeatedly use the movement amount (Δ x1, Δ y1, Δ θ 1) determined by the adjustment amount board in step 208. In subsequent steps 209, 210, printing, moving, removing, etc. of the circuit board 153 is performed. In step 211, it is determined whether the printing operation of the circuit board 153 is to be continued. If printing continues, repeat steps 207 to 210 above; otherwise, the work is finished.

In this embodiment, the stage 1 is moved toward the mesh plate 121. However, it is not necessarily limited to such an arrangement, and the mesh plate 121 may be moved toward the stage 1 as well, or both.

In the present embodiment, in order to calculate the adjustment amount and the movement amount of the stage 1, it may be arranged that: the coordinate position of the midpoint of the coordinate positions of the two

meshes

122, 123 on the mesh plate 121 and the coordinate position of the midpoint of the coordinate positions of the two contact points 151, 152 on the adjustment amount circuit board 150 may be used. However, the determination of the coordinate position is not limited to the coordinate position of the midpoint.

Further, to determine the angles θ s1, θ p1, the X-axis is used as a reference line, but not limited thereto, and there are other possibilities, for example, the Y-axis or any straight line is used as a reference line.

Further, in the above-described embodiment, a method is employed in which: so that the centers of the mesh of the selected screen plate 121 and the contact point of the adjustment amount circuit board 150 coincide with the intersection 111A of the display device 111. But is not limited thereto, that is, the operator may select the mesh and the contact point to be circular, square and rectangular. Accordingly, the control device 110 may control to automatically measure the selected mesh and the midpoint of the contact point by two pointers (+)112 provided through the display screen of the display device 111, as shown in fig. 4. Similarly, the above operation can be performed by moving the pointer 112 to the upper right and lower left of the mesh or the contact point, or by moving the pointer 112 to the left corner point, the right corner point, or the upper corner point, the lower corner point of the mesh or the contact point. In this way, the operability of the operator can be improved.

In the present embodiment, the printing is completed with the adjustment amount calculation circuit board 150. The adjustment amount calculation circuit board 150 may be a circuit board that is not conditioned by printing, and is only intended to determine the adjustment amount of the movable stage 1.

In another simplified embodiment of the present invention, as shown in fig. 13, the adjustment amount calculation circuit board may not be used. That is, the screen printing method of the present embodiment is performed by a screen printing apparatus including a screen 121 and a stage 1, in which the circuit boards are sequentially mounted on the same mounting position of the stage at the board loading/unloading position 182 so that the circuit boards and the screen do not overlap each other; at least one of the object stage and the screen plate can move so that the screen plate and the circuit board can be mutually overlapped; the solder paste on the screen may be printed onto the circuit board in sequence. The screen printing method comprises the following steps:

recognizing a mounting position of the screen with respect to one recognition reference point 181(S302) when the screen is mounted to the screen printing apparatus;

identifying a mounting position of the circuit board on the stage with respect to an identification reference point (S302) when the circuit board 150 is mounted on the stage;

calculating the position adjustment amount of the screen plate and the circuit board according to the mounting position on the identified screen plate and the mounting position on the circuit board (S304); the stage or the screen is moved so that the screen and the circuit board overlap each other in consideration of the adjustment amount, and the solder on the screen is printed on the pattern printing position of the circuit board (S308-309). Steps S301 and S310 in the embodiment of fig. 13 correspond to steps S201 and S210, respectively, in the first embodiment of fig. 1. In step 311, it is determined whether to continue printing on the circuit board 153. If printing continues, repeat steps 301 to 310 above; otherwise, the work is finished.

In the screen printing method of fig. 13, the mounting position of the screen can be identified by a method of detecting any two different points on the screen and calculating the positions of the two points with respect to the reference point; also, the placement position of the circuit board can be identified by a method of detecting arbitrary two points on the circuit board and calculating the positions of the two points with respect to the reference point. In FIG. 13, the two different points on the web sheet are any two meshes on the web sheet; the two different points on the circuit board are any two contact points on the circuit board

In fig. 13, given a reference state where the solder on one screen has been printed to the position of the pattern on the board that should be printed, the adjustment amount is calculated based on: according to the displacement between the screen plate position and the screen plate installation position in the reference state; a displacement between the position of the circuit board in the reference state and the placement position of the circuit board.

In these embodiments, there is a case of printing on a circuit board as an example. But not limited to, solder paste, may be replaced with a viscous liquid such as an adhesive for use on a circuit board.

As described above, according to the screen printing method and the screen printing apparatus of the present embodiment, the calculated movement adjustment amount includes the movement adjustment amount of the stage 1 with the adjustment amount calculation circuit board 150, and the movement of the stage 1 is controlled by the movement amount determined by the adjustment amount calculation circuit board 150 without calculating the movement amount for each circuit board 153, 153 in turn. Thus, the printing operation can be performed at a higher speed than conventional devices. Furthermore, the mesh and the contact points on the screen 121 and the adjustment amount circuit board 150 can be photographed by the recognition camera 2; the coordinate positions of the mesh and the center of the contact point, for example, the distance from the recognition reference point 181 to the mesh, the center position of the contact point, may be calculated by the display device 111. Therefore, the screen printing method and the screen printing apparatus can be applied to a screen and a circuit board without an identification mark as well.

As described in detail above, according to the screen printing method and the screen printing apparatus according to various aspects of the present invention, the adjustment amount of the movement of the stage can be calculated by using one circuit board, and the movement of the stage can be adjusted according to the determined adjustment amount in the subsequent printing operation without calculating the adjustment amount for each circuit board of the same kind. Thus, the operation can be performed at a higher speed than the conventional apparatus.

The present invention is a Japanese patent application No. 8-154332 filed on 1996, 6/14/comprising a specification, a claim, a drawing and an abstract, which are embodied as a whole by the specification.

Although the preferred embodiments of the present invention have been described in detail hereinabove with reference to the accompanying drawings. It should be noted that various obvious modifications and changes can be made by persons skilled in the art. Such changes and modifications are to be considered as included within the scope of the present invention, unless otherwise noted, and various changes and modifications will become apparent to those skilled in the art. Such changes and modifications, as defined by the appended claims, are intended to be within the scope of the invention as defined by the claims, unless such changes depart from the scope of the invention.

Claims

1. A method of screen printing comprising the steps of:

placing a circuit board (150) on a mounting position of a stage (1) of a screen printing apparatus so that the circuit board (150) does not overlap a screen (121) of the screen printing apparatus;

when the screen plate (121) is placed, the installation position of the screen plate (121) relative to an identification reference point (181) is identified by detecting any two different points on the screen plate (121) and calculating the positions of the two points on the screen plate (121) relative to the identification reference point (181);

when the circuit board (150) is placed on the stage (1), identifying a placement position on the circuit board (150) relative to the identification reference point by detecting two different points on the circuit board (150) corresponding to two points on the screen (121) and calculating the positions of the two points on the circuit board (150) relative to the identification reference point (181);

calculating a position adjustment amount for re-placing at least one of the screen (121) and the circuit board (150) according to the identified mounting position of the screen and the placing position of the circuit board (150); and

moving at least one of the stage (1) and the screen (121) such that the screen (121) and the circuit board (150) overlap each other; wherein at least one of the stage (1) and the screen (121) is moved in accordance with a position adjustment amount each time the same type of circuit board (150) is placed on the stage (1);

applying a flux on the screen (121);

the solder is printed from a screen (121) onto a circuit board (150) which is overlapped with the screen (121).

2. A screen printing method according to claim 1, wherein said two different points on the screen are any two openings on the screen.

3. A screen printing method according to claim 1 or 2, wherein said two different points on the circuit board are any two contact points on the circuit board.

4. A screen printing method according to claim 1 or 2, wherein given a reference state where solder on a screen is printed to a position of a pattern which should be printed on a circuit board, the adjustment amount is calculated based on:

the displacement between the position of the circuit board and the position of the screen plate in the reference state.

5. A screen (121) printing apparatus comprising:

a mesh plate (121);

a stage (1) for placing the circuit board (150);

a moving means for moving at least the stage (1) and the screen (121) so that the screen (121) and the circuit board (150) mounted by the stage (1) overlap each other, and

a printing device for printing the solder of the screen (121) onto the circuit board (150),

an image pickup device (2) for recognizing a mounting position of the screen plate (121) with respect to an identification reference point (181) by detecting any two different points on the screen plate (121) and calculating positions of the two points on the screen plate (121) with respect to the identification reference point when the screen plate (121) is mounted, and for recognizing a mounting position of the circuit board (150) with respect to the identification reference point by detecting two different points on the circuit board (150) corresponding to the two points on the screen plate (121) and calculating positions of the two points on the circuit board (150) with respect to the identification reference point when the circuit board (150) is placed on the stage (1); and

a control device (110) for calculating a position adjustment amount for repositioning at least one of the screen (121) and the circuit board (150) based on the recognized mounting position of the screen (121) and the mounting position of the circuit board (150), and if the same type of circuit board (150) is placed on the stage (1), the moving means moves at least one of the stage (1) and the screen (121) based on the adjustment amount

6. A screen printing method according to claim 5, wherein said two different points on the screen (121) identified by the image capturing device are any two openings in the screen.

7. A screen printing method according to claim 5 or 6, wherein said two different points on the circuit board identified by the image capture device are any two different contact points on the circuit board.

8. A screen printing apparatus according to claim 5 or 6, characterized in that when a circuit board is placed on the stage (1), said image pickup device (2) is moved to acquire image data of an arbitrarily selected position on the screen and an arbitrarily selected position on the circuit board to identify a screen placement position with respect to an identification reference point (181) and a circuit board placement position with respect to the identification reference point.

9. A screen printing apparatus according to claim 5 or 6, wherein said control device (110) is adapted to calculate at least one adjustment amount for the screen and a part of the circuit board where the solder paste on the screen is to be printed on the pattern printing position on the circuit board, wherein the calculation of the adjustment amount is performed based on a displacement between the position of the screen in the reference state and the mounting position of the screen and a displacement between the position of the circuit board in the reference state and the mounting position of the circuit board, given a reference state where the solder paste on the screen is to be printed on the pattern position on the circuit board.